US2013777A - Rotary compressor - Google Patents

Description

Sept. 10, 1935. I J. H. DENNEDY 7 ROTARY COMPRESSOR Filed June 24, 1 931 2 Sh'eeis-Sheet 1 .7 w .51 J me; fiergrzeay g E/ 1 49 777%4MM P 1935- J. H. DENNE-DY 2,013,777

ROTARY COMPRESSOR Filed June 24,. 1931' 2' Sheets-Sheet 2 Patented Sept. 10, 1935 no'ranr comrmssonv llames H. Dennedy, Evansville, Ind assig'nor to Rotorite Corporation, Chicago, 111., a' corporation of Illinois Application June 24, 1931, Serial No. 54 6.533

12 Claims.

This invention relates to a rotary compressor and will be described as incorporated in a refrigerating system for the compressing of refrigerant gas.

'An object of this invention is the provision of such a compressor which will operate quietly and smoothly and with the consumption of a minimum amount of power.

In the prior constructions of rotary compressors using radially extending vanes slidably mounted. in slots in the rotor and adapted to be pressed against the wallet the stator or casing by centrifugal force, there hasbeen a very objectionable chattering of the vanes and a lag in'the movement of the vanes outwardly to their extreme outer position because of the tendency for a vacuum to be created in the slots behind the vanes. Such diificulties and objectionable operation are undesirable, not only for the reason of noise and vibration, but because of the decided reduction in efliciency caused by the escape of fluid backwardly by the vanes. This also results in the necessity of using greater power to drive the compressor for overcoming additional friction and it results in a very great reduction in the compressing capacity of a compressor of predetermined dimensions and speed of rotation.

- In rotary compressors of the type herein set forth, various mechanical devices have been employed to force the vanes outwardly such, for instance, as springs or pins extending between opposite vanes. Such mechanical devices have been found in actual practice tobe noisy and ine fli cient. The vanesin such compressors must be.

closely fitted tothe slots in order to prevent leakage. When a close fitting vane is placed in a slot, and particularly. so when an abundance of oil is present as in rotary compressors, there is a tend ency upon rotation of the'vanes for the vanes to move outwardly under centrifugal force but in so moving the vane. creates a vacuum in the bottom of the slot. I have found in practice that this vacuum is sufllcient to overcome the centrifugal force and prevent the vane from moving outwardly and for this reason pins or springs have been .used to push the vanes outwardly.

When the vanes are resting on the bottoms or the slots, and pins or springs are not employed, there are no spaces under the vanes and the slightest movement of the vanes outwardly croates a very high vacuum. I have overcome this obj ti n y mploying pace behind the vanes so that slight movement outwardly will not crethe pressure in such space. A direct vent from scription.

one slot to the opposite slot 'causes noise and decreases the eiilciency of the compressor. I-have overcome this dimculty by the use of high resistance passageways connecting the various slots, as will be hereinafter more particularly described. 5

It is the object of my invention to'provide an improved compressor which overcomes the foregoing objections.

Other objects and advantages of my improved construction will appear from the following de- 0 In the accompanying drawings, Fig. 1 is a vertical longitudinal section taken' through a. refrigerating unit and compressor incorporating my invention and more particularly taken on substantially the line l--l of Fig. 2; Fig. 2 is a vertical section taken partially on the line 2-2 of Fig; l and partially offset into the plane of the intake port; I

Fig. 3 is a longitudinal section through the rotor, taken on the line 3-3 of Fig. 4, with the compressor vanes omitted and showing-a'portio of the rotor in elevation: and I Fig. 4 is a vertical section taken on the line 8-4 of Fig.3 and showing the compressor vanes in position and in section.

My improved compressor is'illustrated in the drawings as incorporated in a refrigerating unit comprising a casing 2 having an open end which is normally closed by a casting 3. A suitable gasket 4 is interposed between the casing 2 and. the casting 3 to form'a fluid-tight sealto prevent' the escape of gas and oil from the interior of the casing. The casing is normally partly fllledwith oil 5 to substantially the levelindicated mm. 1.

The oil is adapted to pass out ofthe casing .through a'discharge line including a conduit 6, a fitting I, a bore 8 in the casting 3, a fitting 9, an elbow Ii, and a conduit l2. Oil is normallyintroduced into the casing 2 through a conduit 40 I3 and associated conducting elements terminat-- ing in a duct M which discharges into the space I! within the, compressor casing or stator l8.

.The oil is discharged'from the compressor through the discharge conduit I'I directly into the casing 2 which normally contains refrigerant under high pressure.

Low pressure reirigerant is admitted to the .compressor through a conduit l8, upwardly through a fitting it, past the check valve 21 com prising a water and a ball .22 held on the water by gravity, and through a passageway 23, and

opening into a' plurality of relatively wideate a high vacuum but will at most only reduce mouthed inlet ports 24 to the space between the 5 rotor '25 and the compressor casing. The refrig- 5 into the casing 2 from which it passes through erant is compressed by the vanes 28 and discharged through the discharge port ll directly the separator 28 and outwardly through the discharge portion 28 thereof and through the discharge conduit 3| for use in a refrigerator not illustrated.

The compressor consists of a cylindrical stator or casing l6 which is open at both ends and when assembled is normally closed at one end by engagement with the inner surface of the casting 3 and at the other end by engagement with a casting 32 having a cover plate 33 thereon and firmly held in position by the bolts 34 and 35 which pass directly through the compressor casing for holding the same upon the face of the casting 3. The rotor 25 preferably consists .of a single cylindrical element which has a reduced portion 38 at one end journaled in a bearing 31 and passing through the same. The extreme outer end of the portion 36 is provided with a fluid seal 38 and a nut 39 which is adapted to receive driving force from any suitable source of power. The other end of the rotor 25 is provided with a reduced portion 4| journaled in a bearing 42 in the member 32. The end of the bearing 42 is sealed by the cover plate 33 to prevent the passage of fluid between the interior of the casing and theinterior of the compressor through the bearing 42.

The rotor is provided with a plurality of slots" 43 which preferably extend longitudinally parallel with the axis of the rotor and which also extion. From the reduced portion 4| of the rotor backwardly through the body of the rotor is provided a substantially cylindrical bore 41 passing along the axis of the rotor. The bore 41 is preferably cylindrical and is provided with a pin 48,

which pin is preferably a prism and in the drawings is shownto be square in cross-section. The corners of the pin 48 very tightly engagev the surface of the passageway 41 in a manner such that the pin 48 is very snugly circumscribed by the passageway 41 to provide a plurality ofpassages 49, one along each flat side of the pin 48. The inner end of the pin 48 is tightly pressed against the bottom of the bore forming the passageway 41 to prevent the passage of fluid from one of the passages 49 to the others at the inner end thereof. The outer end of the pin 48 does not extend to the outer end of the passageway 41 but leaves a portion through which intercommunication is permitted between the passages 49. Each of the passages 49 communicates with the slots 43 below the vanes 26 through radially extending ducts 5|. The ducts 5| are preferably relatively small in cross-section to form a resistance to the passage of fluid therethrough.

This construction places each slot into com munication with the other slots by means of a passage having a high frictioned resistance, but

I at the same time permits the outward movement of the vanes from causinga vacuum to be formed arcuate spaces between the vanes of the compressor are subjected to-increasingly high pressure as the space approaches the discharge port in rotation. This subjects the oil which has been injected into the space to an increasing pressure tending gradually to seep or work its way betweenthe blade and slot into the passages which interconnect the slots. If any refrigerant has found its way into these passages, the oil will thus displace it.

.I do not, however, employ a lubricant feed to the slot interconnecting passages, in the sense that the term feed is usually applied. Any flow of the oil from the compressor easing into the,

passages within the rotors is a very gradual seepage and, as it will be observed, not one which subjects the passages to any prevailing liquid pressure from without. In the specific instance of the four vanes here shown, the sum of the displacements per degree of rotation for the two in-moving vanes is the samev asthat for,the two outmoving varies, and this is true for most vane type compressors.- The hydraulic interconnection of the vane slots by the oil passages in the rotor constitutes virtually a closed hydraulic transmission system having a constant volume. This constant volume ismaintained, because, as explained, as

certain of the blades movein, the others correspondingly move out.

Ordinarily centrifugal force will cause the blades to move outwardly in their slots and the camming action of the eccentric mounting will push them in again. When there is no sticking of the vanes, the lubricant will surge back and forth through the slot-interconnecting passages with compartively slight pressure. There is comparatively little danger of a vane sticking when it should move inwardly, for the camming action of the slidably eccentric mounting of the rotor in the casing is so power ful. But if a vane were to stick in its innermost position whenit should move, out under centrifugal force, then the two vanes which happen to be moving in at the moment will build up pressure under the powerful force of the camming action against the in-moving vanes. A very high pressure will then be built up almost instantaneously and much faster than it can be relieved by any leakage between the vanes and the slots. Thus if a vane sticks, a pressure will automatically be 'built up to whatever force is necessary to move the vane. But such a pressure will not be built up unless a vane does stick, and the pressure will be built up only to the amount required to make the sticking vane move.

Afclosed hydraulic interconnection of the vanes s has greater advantage over a liquid interconnection of the vanes which might be described as an open or "feed system where, for instance, the end of the center bore of the rotor is freely connected with a conduit leading from the oil reserve 5. In the latter case each vane would always be subject to a continuous hydraulic pressure, thereby putting unnecessary wear on the outer edge of the vane and on the bore of the compressor. If a vane were to stick, it would then be impossible to build up any additional pressure to relieve it, for any additional pressure developed by the in-moving vanes would merely back up against the feed If the constant feed pressure were to be increased to a point where it was calculated to relieve most of the danger of sticking vanes, it-would be at the expense of greater wear due to friction and greater operating expensedue to additional power required to satisfy the additional heat of friction. There is also an advantage in having each vane hydraulically interconnected with all of the other vanes rather than-being connected merely with its opposite vane. One advantage is that the burden of building up pressure necessary to move a sticking vane is distributed between two inmoving vanes instead of being concentrated upon only one in-moving vane. This makes for better wear and less vibration in the event that a chronically sticking vane develops.

There' is also considerable advantage in the use of the long restricted passages afforded by the faces of the prismatic pin 48 in interconnecting the vane slots, although I contemplate that my compressor will operate satisfactorily in many cases-especially where .quiet operation is not so essentialwithout any pin 48 in the axial bore of the rotor. The reason that the long restricted liquid passages interconnecting the slots is of advantage is this: In the rotation of the rotor, each vane atone point passes over and momentarily closes oi! the oil feed duct II. The oil in this passage is under considerable pressure. At

the instant the duct [4 is closed by the edge of a vane, the oil in the duct, partly because of its prevailing pressure and partly because ofa hydraulic ram-like action, tends very abruptly to pushalmost knock-the vane inwardly. If the inner end of the vane were too frcely'hydraulical- ,ly interconnected with the other vanes, it would transmit a momentary vibration to them, in-

creasing the friction of their outer edges against Y the bore of the casing. For this reason and perhaps other reasons, a condition best described as "chattering develops. I have found that if the vane slots are not toofreely interconnected but only through long and restricted passages, a sufflcient fluid resistance is built up in the passages to cushion the knock, with the resultthat the chattering is avoided. A prism having as many faces as there are blades, inserted in an axial bore of the rotor with its longitudinal edges sealed against the bore provides a peculiarly simple, economical and convenient expedient for effecting such a connection. a

' If the ducts interconnecting the vane slots were of large flow capacity, when a given slot came into the high pressure are of its revolution, the high pressure would expel some of the lubricant along the working passages between the vanes and their slots (which result from the inherently somewhat loose fit in which the lubricant is normally intended to seal) toward the corresponding working clearance of the opposite vane in the low pressure are. cant would be expelled into the chambers adjoining that opposite slot. The amount of this leakage would, of course, increase with the age of the compressor and the attendant wear increasing the clearance between the vanes and the slots. The objection to such introduction of lubricant into the compartments at the low pressure or inlet arcs is that to the extent the compartments or chambers between the blades'are filled with lubricant the capacity for gas is reduced.

The restriction which I'place in the passages As a result a considerable quantity of lubriinterconnecting the slots reduces the effective flow capacity between slots to a restricted flow much less than that permitted .by the clearance between the vanes and the'slots. Consequently the lubricant leakage between the high pressure region 5 and the low pressure region through the rotor is so materially reduced by my restricted passages that thelessening of the gas capacity of the com- .pressor is reduced to a harmless minimum.

, similarly,-ip referring .to the restricted passages in the rotor being considerably longer than the. distance between the slots, I mean a character of passageway in which the passageway is greatly elongated over that which would otherwise be employed in providing a free and ready conduc- 1 tion of liquid between the slots; that is, where the additional length is provided for the purpose of restricting communication.

From the foregoing description it will be readv ily appreciated that certain changes and modifications can be made in this improved compressor without departing from the principle of my invention, and I therefore desire to avail myself-' of any such modifications as come within the scope of the appended claims:

-I claim:

1. In a fluid compressor, in combination, a cylindrical casing, a cylindrical rotor in said casing, said rotor being ,Journaled on, its axis eccentrically of the axis of the casing, intake and discharge ports in said casing, said rotor having a plurality of longitudinally extending slots therein, compressor vanes'slidably fitted in said slots 40 for sweeping the inner surface of the casing when rotated, said rotor having a longitudinally extending passageway and ducts connecting the slots with the-passageway, and a prism-shaped element circumscribed by the surface of the pas- 'sageway forming a plurality of interconnected passages for resisting the passage of fluid therethrough.

ports, and having a lubricant feed duct in its circumferential wall, a cylindrical rotor of smaller diameter than said casing Journaled parallel with the axis of the casing to engage the circumfercntial wall thereof, said rotor having longitudinal slots, slidably mounted vanes in the slots adapted to slidably engage the inner surface of the casing when rotated, said rotor having a longitudinally extending passageway and ducts connecting the slots with the passageways, and a prism shaped element circumscribed by the surface of the passageway, thereby forming a plurality of interconnected passages for resisting the passage of fluid therethrough. v

3. In a rotary compressor, in combination, a cylindrical casing having intake and) discharge ports, andhaving alubricant feed duct in its circumferential wall, a cylindrical rotor of smaller diameter than said casing journaled parallel with the axis of the casing to engage the circumferential wall thereof, said rotor having longitudinal slots, slidably mounted vanes in the slots adapted to slidably engage the inner surface of the casing when rotated, said rotor having a longitudinally extending passageway and ducts connecting the slots with the passageways, and a pin in said passageway engaging the inner surface thereof along parallel lines, and spaced therefrom at intermediate points to form a plurality of interconnected restricted passages communicating with said ducts.

g. In a rotary fluid compressor, in combination, a casing having a cylindrical inner surface, said casing having intake and discharge ports and an oil feed duct spaced circumferentially from said ports, a cylindrical rotor of smaller diameter than the casing and of alength to snugly fit therein, said rotor being journaled on its axis parallel with the axis of the casing and engaging the circumferential inner surface of the casing between the discharge and intake ports, said rotor having radial slots extending longitudinally thereof, compressor vanes slidably fitted in. said slots and adapted to be urgedagainst the casing by centrifugal force and-sweep the same when the rotor is rotated, said rotor having a cylindrical passageway extending longitudinally thereof,

a non-cylindrical pin shorter than. the passageway tightly fitted in the passageway and having uninterrupted contact with the surface of the passageway along a plurality of'parallel lines, thereby forming restricted passages along the sides of the pin, and ducts leading from the passages to the bottoms of the slots.

5. In a rotary fluid compressor, in combination, a casing having a cylindrical inner surface, said casing having intake and discharge ports and an oil feed duct spaced eircumferentially from said ports, a cylindrical rotor of smaller diameter than the casing and of a length to snugly fit therein, said rotor being journaled on its axis parallel with the axis of the casing and engaging the circumferential inner surface of the casing between the discharge and intake ports, said rotor having radial slots extending longitudinally thereof, compressor vanes slidably fitted in' said slots and adapted to be urged against the casing by centrifugal force and sweep the same when the rotor is rotated, said rotor having a cylindrical passageway extending along its axis and closed at one end, a square pin tightly circumscribed by the surface of the passageway and tightly, pressed against the body of the rotor at the closed end of the passageway, thereby forming a plurality of small passages along the sides of the pin, said pin being shorter than the passageway to permit intercommunication of the passages at one end of the pin, means forpreventing the escape of fluid from the end of the passageway, and ducts in the rotor providing communicationbetween the bottom of each slot and a corresponding passage along said pin.

6. A gas compressor comprising a body having a cylindrical bore, a rotor eccentrically journaled within the bore, radial slots in the rotor, means forming arcuately offset inlet and dischargeports for the gas, vanes radially slldable in the slots, an inlet port for liquid lubricant under high pressure communicating with the bore and swept by the outer edges of the vanes, an axial system of elongated restricted passages each connected to a slot inwardly of the vane said passages intercommunicating at one end confining lubricant and providing restricted paths' for said lubricant whereby'the impact'given the outer edge of one vane in passing said lubricant port is dampened in hydraulic communication through said passages to another vane.

7. A gas compressor comprising a body having a cylindrical bore, a rotor eccentricallylournaled sure communicating with-the bore and swept by 5 I the outer edges of the vanes, liquid lubricant filled passage means interconnecting the slots inwardly of the vanes and confining the lubricant communication therebetween to restricted 1 paths whereby the impact given the outer edge of one vane in passing said lubricant portisdampened in hydraulic communication through said paths to another vane, said passage means comprising an axial longitudinally extending passage in the rotor included in said path. 8. A compressor rotor having, a plurality of longitudinally extending radial slots, vanes radially slidable therein, a cylindrical bore extending axially of the rotor and ducts communicating between the respective slots, inwardly of their vanes, with the bore through its cylindrical surface, and a prism, having as many sides as there are slots, within the bore with its edges forming fluid seals with the surface of the bores to form longitudinal passages of segmental cross section, each of the passages communicating with one of the ducts, respectively, each passage communicating with at least one other passage to confine inter-slot communication to paths. along said. passages.

9. A gas compressor comprising a body having a cylindrical bore, a rotor eccentrically journaled therein, means forming inlet and outlet gas passages for the compressor, radial slots in the rotor,

vanes in the respective slots and slidable radially therein with the outer edges sweeping the bore of the body, a liquid-lubricant inlet port lead-.- ing from a source of lubricant under high pressure and communicating with the bore and swept by the outer edges of the vanes, and means af- 40 fording a cushioned hydraulic communication between the inner edges of the vanes, comprising an axial bore of circular cross section in the rotor, a duct communicating between each. slot and the axial bore, and a prism inserted in the i5 bore with its edges sealing against the cylindrical surface thereof and having as many sides as there are slots, leaving longitudinal segmental passages, one of which faces each duct, and means forming a communication between the respective passages longitudinally spaced from their ducts, whereby fluid communication between each slot, and another slot is confined to longitudinal paths through two of said passages, said passages and ducts beingfilled with liquid lubricant and constituting a closed hydraulic system.

' 10. In a gas compressor, in combination a cylindrical casing, a cylindrical rotor in the casing, said rotor being journalled on its axis eccentrically of the axis of the casing, intake and discharge ports in said casing, said rotor having a plurality of longitudinally extending radial slotstherein, compressor vanes slidably fitted in the slots for sweeping the inner surface of the casingwhen rotated, and constructed and arranged to form compartments therebetween which ensmall' in rotating from the inlet port to the discharge port, relatively long flow resisting liquid lubricant filled communicating passage means in the rotor 1 between the respective slots constituting a closed liquid system confining inter-slot lubricant flow eccentrically in said bore, said rotor having a plurality of arcuately spaced slots and a plurality of compressor vanes mounted in the respective.

slots for sweeping contact with the bore of the casing, the rotor defining passages interconnecting said slots, said passages and the slots, inwardly of the vanes, constituting a closed liquid system kept filled with liquidlubricant seeping thereinto, said vanes being urged outwardly during rotation solely by centrifugal force and the pressure of said liquid system, the inward movement of one of said vanes exerting avpressure on the lubricant in said passages to aid centrifugal force in urging another of said vanes outwardly.

12. A rotary gas compressor comprising a compressor casing having a bore, a rotor mounted eccentrically in said bore, said rotor having a plurality. oi. .arcuatelv spaced radial slots and a plurality of vanes radially slidable in the respective slots, arcuately spaced inlet and discharge ports in the casing, gas chambers defined between the arcuately spaced vanes ensm'alling in rotating ,from the inlet port to the discharge port, and

high resistance passageways formed in the rotor interconnecting the slots and filled with liquid lubricant constituting a closed hydraulic system, 10

means for supplying liq'uid lubricant to the rotor for seepage into said system the vanes being urged radially outwardlysolely by centrifugal force and the pressure of said hydraulic system.

JAMES H. DENNEDY.

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